Pressure Output Device For Extracorporeal Hemodialysis Machine

ABSTRACT

A pressure output device (POD) assembly for sensing fluid pressure in a fluid processing system, is provided. This POD assembly includes a shell defining a shell interior, and a movable diaphragm disposed in the shell interior and separating the shell interior into a flow-through chamber and a pressure sensing side. A sensor port is in fluid communication with the pressure sensing side. An inlet port and an outlet port are in fluid communication with the flow-through chamber. The inlet port and the outlet port define an inlet and an outlet, respectively, of a flow-through channel that passes through the flow-through chamber. A boss protrudes from the interior wall of the shell and extends into the flow-through channel to prevent occlusion of flow under different pressure conditions within the flow-through chamber.

This application claims the benefit under 35 U.S.C. §119(e) of priorU.S. Provisional Patent Application No. 62/056,122, filed Sep. 26, 2014,which is incorporated in its entirety by reference herein.

FIELD OF THE INVENTION

The present invention relates to pressure output devices for measuringfluid pressure in an extracorporeal hemodialysis machine.

BACKGROUND OF THE INVENTION

Hemodialysis machines commonly monitor pressure in an extracorporealblood circuit, for example, pressure from a blood chamber containing ablood-air interface. An air-filled tube connects the blood chamber to apressure port of the machine. A transducer protector, containing ahydrophobic membrane, is positioned between the blood chamber and thepressure port. The membrane provides a sterile barrier to the bloodcircuit and prevents blood contamination of the machine, yet allows airpressure to pass through the membrane and act on the pressure transducerinside the machine. Problems with such a blood-air interface systeminclude clotting, heparin dosage concerns, contamination, and inaccuratepressure measurements. Air contact with blood results in clotting thatcan collect in portions of the blood circuit, reducing treatmenteffectiveness. Clotting can also occasionally require replacement of thedialyzer during treatment. To reduce clotting during dialysis, a patientis typically administered a dosage of heparin, sufficient to allowadequate treatment time, yet allow the patient's clotting factor toreturn to normal levels prior to termination of the treatment. The useof heparin adds cost to the treatment and increases the potential forhazardous blood loss. The hydrophobic membrane in the transducerprotector is very thin, and occasionally allows blood contamination ofthe pressure monitoring circuit on the dialysis machine. When thisoccurs, the contaminated portion of the machine must be cleaned andsanitized before the machine can be used again. Occasionally, duringdialysis, abrupt pressure changes in the blood circuit, or air leaks inthe pressure port connection, allow the blood level to reach thehydrophobic membrane in the transducer protector. Blood contact with themembrane occludes air channels through the membrane, which can inhibitor prevent pressure transfer to the transducer of the dialysis machine.This condition can reduce the response time of the machine, to pressurechanges, or can prevent pressure monitoring completely.

SUMMARY OF THE INVENTION

According to one or more embodiments of the present invention, a liquidprocessing circuit including a pressure output device, is provided. Thecircuit can be an extracorporeal hemodialysis circuit including apressure measuring device, which facilitates many functions. Thepressure measuring device can communicate blood circuit pressure to thepressure port of an extracorporeal blood processing machine, forexample, to a hemodialysis machine, without exposing the blood circuitto air. The device can minimize the potential for hazardous restrictionof blood flow through the blood side of the device, duringpressure-related fault conditions. The device can accurately communicatearterial pressure, for example, in the range of from 0 to −300 mmHg, atelevations of up to 8000 feet. The device can accurately communicatevenous pressure, for example, in the range of from 0 to 500 mmHg, atelevations of up to 8000 feet. The device can prevent bloodcontamination of the pressure monitoring circuit on a hemodialysismachine. In addition, the device can prevent contamination of the bloodcircuit.

The pressure output device (POD) assemblies of the present invention canbe placed along and used in the arterial and venous lines of anextracorporeal circuit, for example, of a dialysis machine, to be usedduring hemodialysis. The POD assembly provides an airless system fortransferring extracorporeal circuit pressures to pressure monitoringports of the extracorporeal circuit, for example, to the ports of ahemodialysis machine. Each POD assembly has two chambers that areseparated from one another by an elastomeric diaphragm. Each chamber canbe translucent. Blood can flow through one of the chambers, referred toherein as the flow-through side or chamber of the POD assembly. A volumeof air can be contained in the second chamber. As blood flows throughthe flow-through side of the POD assembly, positive or negative circuitpressure displaces the diaphragm. The respective displacement of thediaphragm compresses or expands the volume of air between the diaphragmand the pressure transducer in the hemodialysis machine, with which thevolume of air is in fluid communication. As the air volume changes, theresulting pressure will be detected by the pressure transducer. The PODassembly also protects the pressure transducer from blood contact, andprovides a sterile barrier at the interface to the blood circuit. Usingthe POD assembly of the present invention eliminates the need for atypical transducer protector, including the need for a hydrophobicmembrane. The present invention thus also eliminates the problemsmentioned above that are associated with the use of a typical transducerprotector.

The flow-through side of the POD assembly has two ports, an inlet portand an outlet port. Each port can be solvent-bonded to flexible tubing,such as polyvinylchloride (PVC) tubing, in an extracorporeal circuit.The tubing ports facilitate blood flow through the flow-through side orchamber of the device. The flow-through side also has an internaldiamond-shaped boss feature that prevents the diaphragm from occludingblood flow that could potentially cause hemolysis duringpressure-related fault conditions.

The second chamber in the POD assembly is referred to herein as thepressure sensing side of the POD assembly. The pressure sensing side hasa single port, also referred to as a sensor port, that can besolvent-bonded to flexible tubing. The flexible tubing can attach, via aluer fitting, to a pressure monitoring port of a hemodialysis machine.Both chambers in the POD assembly can be designed with internal volumesto facilitate accurate output of arterial pressures, for example, withina range of from 0 to −300 mmHg, and venous pressures of from 0 to 500mmHg, even at elevations of up to 8000 feet above sea level. Otherdesigns or volumes can be used to achieve any suitable and/or desiredrange of pressure sensing, whether for sensing arterial pressure, venouspressure, or any other kind of fluid pressure. Atmospheric pressure andchamber volumes can be directly related to the operating range forpressure output, and in extreme conditions, such as altitudes in excessof 8000 feet, customized or tailored chamber volumes can be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be even more fully understood with thereference to the accompanying drawings which are intended to illustrate,not limit, the invention.

FIG. 1A is a cross-sectional side view taken through the middle of apressure output device (POD) according to one or more embodiments of thepresent invention, showing the POD assembly configured for measuringarterial blood circuit pressure and the POD assembly diaphragmpositioned at 0 mmHg.

FIG. 1B is a cross-sectional side view of the POD assembly shown in FIG.1A and indicating the directional movement of the diaphragm as pressuredecreases in the arterial blood circuit.

FIG. 1C is cross-sectional side view of the POD assembly shown in FIGS.1A and 1B but wherein the diaphragm is positioned at the most negativeaccurately measurable arterial pressure, i.e., at sub-atmosphericpressure of −300 mmHg.

FIG. 2A is a cross-sectional side view taken through the middle of apressure output device (POD) according to one or more embodiments of thepresent invention, wherein the POD assembly is configured to measurepositive pressure in a venous circuit and the POD assembly diaphragm ispositioned at 0 mmHg.

FIG. 2B is cross-sectional side view of the POD assembly shown in FIG.2A and indicating the directional movement of the POD assembly diaphragmas pressure increases in the venous blood circuit.

FIG. 2C. is a cross-sectional side view of the POD assembly shown inFIGS. 2A and 2B but wherein the diaphragm is in a position that resultsfrom exertion of maximum venous pressure.

FIG. 3 shows the location of an arterial POD assembly and a venous PODassembly in an extracorporeal circuit of a hemodialysis machine,according to one or more embodiments of the present invention.

FIG. 4A is a top, left perspective view of an assembled POD, alsoreferred to as a POD assembly, according to one or more embodiments ofthe present invention.

FIG. 4B is a top, left perspective view of the cap of the POD assemblyshown in FIG. 4A.

FIG. 4C is top, left perspective view of a diaphragm that can be usedaccording to one or more embodiments of the present invention, anduseful in the POD assembly shown in FIG. 4A.

FIG. 4D is a top, left perspective view of the base of the POD assemblyshown in FIG. 4A and showing a boss, according to one or moreembodiments of the present invention, interrupting the flow path throughthe flow-through chamber of the POD assembly.

FIG. 4E is a top plan view looking down on the POD assembly base shownin FIG. 4D.

FIG. 5 is an enlarged view of an exemplary boss that can be formed in aPOD assembly base, according to one or more embodiments of the presentinvention.

FIG. 6A is a cross-sectional side view of an arterial POD assemblyaccording to one or more embodiments of the present invention andshowing the POD assembly diaphragm position at the start of a treatment.

FIG. 6B is an enlarged view of section 6B shown in FIG. 6A, illustratingdetails of the hinge of the diaphragm, and showing the engagement of thePOD assembly components with one another.

FIG. 6C is a cross-sectional end view of the arterial POD assembly shownin FIG. 6A.

FIG. 6D is an enlarged view of section 6D shown in 6A illustratingdetails of one of the two hinge interruptions in the POD assemblydiaphragm.

FIG. 7A is a cross-sectional side view of a venous POD assemblyaccording to one or more embodiments of the present invention andshowing the POD assembly diaphragm at a treatment start position and thebulge in the diaphragm caused by the diaphragm hinge and hingeinterruptions.

FIG. 7B is a cross-sectional end view of the venous POD assembly shownin FIG. 7A.

FIG. 8A is a cross-sectional side view of the venous POD assembly shownin FIGS. 7A and 7B, but at pressures near 0 mmHg, and showing that thebulge appearing in FIGS. 7A and 7B has been displaced.

FIG. 8B is a cross-sectional end view of the venous POD assembly shownin FIG. 8A.

FIG. 9A is a cross-sectional side view of an arterial POD assemblyaccording to one or more embodiments of the present invention, andshowing the POD assembly diaphragm partially deformed around the boss atthe bottom of the assembly base, due to a pressure fault condition.

FIG. 9B is a cross-sectional side view of the arterial POD assemblyshown in FIG. 9A.

FIG. 10A is cross-sectional side view of the POD assembly shown in FIG.9A but also showing how the base and boss provide a non-occluded bloodflow path despite the pressure fault condition.

FIG. 10B is cross-sectional end view of the arterial POD assembly shownin FIG. 10A but at a pressure fault condition.

FIG. 11A is a top perspective view of the base of a POD assemblyaccording to yet another embodiment of the present invention.

FIG. 11B is a cross-sectional, side view of the POD base shown in FIG.11A.

FIG. 11C is a cross-sectional, end view of the POD base shown in FIG.11A.

FIG. 11D is a cross-sectional, left perspective side view of anassembled POD according to an embodiment of the present invention, andincluding the POD base shown in FIGS. 11A-11C.

FIG. 11E is a cross-sectional, end view of the POD assembly shown inFIG. 11D.

FIG. 12A is a cross-sectional, left perspective side view of a PODassembly according to yet another embodiment of the present invention.

FIG. 12B is cross-sectional, end view of the POD assembly shown in FIG.12A, but wherein the POD assembly is configured for arterial measurementand is shown at zero (0) arterial pressure.

FIG. 12C is cross-sectional, end view of the POD assembly shown in FIG.12A, and wherein, as also shown in FIG. 12A, the POD assembly isconfigured for use as a venous POD assembly and the diaphragm is shownat zero (0) venous pressure.

FIG. 13 is a cross-sectional, end view of yet another POD assemblyaccording to the present invention, configured to sense arterialpressure, and including a telescoping diaphragm shown under zero (0)arterial pressure.

FIG. 14 is a cross-sectional, side view of a POD assembly according toyet another embodiment of the present invention, configured to sensearterial pressure, and including a telescoping diaphragm shown at zero(0) arterial pressure.

FIG. 15 is a cross-sectional, end view of the pressure POD assemblyshown in FIG. 14 but demonstrating the two alternative startingpositions of the diaphragm, including an upper position to be used ifthe POD assembly is configured as an arterial pressure POD assembly, andincluding the lower position to be used if the POD assembly isconfigured as a venous pressure POD assembly.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A-1C are cross-sectional side views of an assembled pressureoutput device (POD) according to one or more embodiments of the presentinvention and arranged to measure blood pressure in an arterial circuit.POD assembly 12 is constructed of a cap 14, a diaphragm 16, and a base18, assembled together. Blood tubing can be connected, for example, bysolvent-bonding, to an inlet port 38 and an outlet port 40 on theflow-through side or chamber of the POD assembly. A sensor port 42 isprovided in cap 14 and tubing can be connected, for example, bysolvent-bonding, to form a communication between sensor port 42 and apressure sensor port of a hemodialysis machine. For the purpose ofsimplification, the respective tubings are not shown in FIGS. 1A-2C.

FIG. 1A shows diaphragm 16 in an initial, start position for an arterialcircuit. POD assembly 12 is arranged to measure negative pressures,i.e., sub-atmospheric pressures. Diaphragm 16 in FIG. 1A is shown aspositioned at zero mmHg. As pressure in the flow-through chamber of PODassembly 12 begins to decrease, diaphragm 16 moves towards theflow-through chamber in the direction shown by arrow P, as shown in FIG.1B.

FIG. 1C. shows diaphragm 16 in a position where it can accurately outputthe most negative arterial pressure, for example, at −300 mmHg. Withdiaphragm 16 in the position shown in FIG. 1C, the pressure-sensing sideof the POD assembly exhibits a maximum volume for accurate measurementand the POD assembly exerts a negative pressure through sensor port 42,which is communicated to a pressure transducer in the hemodialysismachine. More details of the flow-through chamber, the pressure-sensingside, and the arterial POD assembly in general, are provided inconnection with the description of FIGS. 4A-6D below.

FIGS. 2A-2C are side cross-sectional views of a POD assembly accordingto one or more embodiments of the present invention, and arranged tomeasure blood pressure in a venous circuit, that is, arranged to measurepositive blood pressures. FIG. 2A shows a venous POD assembly 120constructed of a cap 114, a diaphragm 116, and a base 118, assembledtogether. While different number reference numerals are used to labelthe components of POD assembly 120, relative to the reference numeralsused to label the components of POD assembly 12 shown in FIGS. 1A-1C, itis to be understood that the exact same components can be used foreither an arterial POD assembly or a venous POD assembly, and only theinitial position of the diaphragm can differ between the twoconfigurations. Accordingly, a set of two POD assemblies can beprovided, and, by proper positioning of the diaphragm, either PODassembly can be configured and used to measure arterial pressure andeither POD assembly can be configured and used to measure venouspressure. A set of two POD assemblies can be provided wherein thediaphragms have already been positioned to be in the initial or startpositions for an arterial POD assembly and for a venous POD assembly,respectively.

Base 118 of POD assembly 120 comprises an inlet port 138 and an outletport 140 to a flow-through chamber of the POD assembly. Cap 114 cancomprise a sensor port 141 on the pressure-sensing side of the PODassembly. More details about the flow-through chamber, thepressure-sensing side, and the venous POD assembly in general, areprovided below in connection with the descriptions of FIGS. 7A-10B.

FIG. 2A shows diaphragm 116 in an initial, start position, at zero mmHg,and configured to measure venous pressure. As pressure increases in theblood circuit, resulting from the flow of blood through the flow-throughchamber of POD assembly 120, diaphragm 116 moves toward cap 114 in thedirection shown by arrow P in FIG. 2B. The movement of diaphragm 116toward cap 114 compresses air in the pressure-sensing side of PODassembly 120, which thereby increases the pressure of gas in the fluidcommunication from the pressure-sensing side, through sensor port 141,and to a venous pressure transducer in a hemodialysis machine. FIG. 2Cshows diaphragm 116 pushing against and flush with the inner surface ofcap 114 at a maximum accurately measurable venous pressure. Adjustmentscan be made to the amount of air in the pressure-sensing side of PODassembly 120 to avoid having diaphragm 116 reach the extreme positionshown in FIG. 2C. Injecting air or gas into the pressure-sensing side,or into a fluid communication communicating with the pressure sensingside, can be used to position diaphragm 116.

FIG. 3 is a schematic view of an extracorporeal blood circuit 300 foradministration of hemodialysis. From a patient, a first arterial tubing302 carries blood to an arterial POD assembly 12, for example, PODassembly 12 shown in FIGS. 1A-1C. A pressure tubing 306, connected tothe sensor port of arterial POD assembly 12, directs a pressure outputfrom POD assembly 12 to an arterial pressure port (not shown) of thehemodialysis machine. Blood flows through the flow-through chamber ofPOD assembly 12 to a blood pump 308, for example, a peristaltic bloodpump. From blood pump 308 blood is moved through a tubing 310 to adialyzer 314. Along tubing 310 a syringe pump 312 is provided, in fluidcommunication with tubing 310. Syringe pump 312 can be a heparin pumpand can be configured to inject heparin into blood circuit 300. For thesake of simplification, dialysate tubings and a dialysate circuit arenot shown connected to dialyzer 314.

Blood exiting dialyzer 314 travels through another segment of tubing toa venous POD assembly 120, for example, venous POD assembly 120 shown inFIGS. 2A-2C. A pressure tubing 316 in fluid communication with thesensor port of POD assembly 120, carries a pressure output to a venouspressure port (not shown) of the hemodialysis machine. Although FIG. 3shows exemplary positions for arterial POD assembly 12 and venous PODassembly 120, it should be understood that the POD assemblies can bearranged at different locations along blood circuit 300. In one or moreembodiments, venous POD assembly 120 is connected directly to the outputof dialyzer 314. In FIG. 3 both arterial POD assembly 12 and venous PODassembly 120 are shown in a vertical orientation as opposed to ahorizontal orientation, which can help prevent the accumulation andtrapping of air bubbles within the POD assemblies.

Blood flowing through the flow-through chamber of venous POD assembly120 exits POD assembly 120 and is carried along another segment oftubing to an air trap and air detector 318. Along a venous return tubing322 that goes from air trap and air detector 318 to the patient, isarranged an air detector clamp 320 that can stop the return of blood tothe patient in the event that air trap and air detector 318 detect airbubbles in the return blood line, i.e., in tubing 322.

As shown in FIGS. 4A-4E, a POD assembly 12 in accordance with one ormore embodiments of the present invention, is provided. POD assembly 12comprises a cap 14, a diaphragm 16, and a base 18. Diaphragm 16 cancomprise a thermoplastic elastomer. Diaphragm 16 can be adhered,frictionally fit to, over-molded, or otherwise contacted onto or withcap 14. Cap 14 can be injection molded, for example, out ofacrylonitrile butadiene styrene (ABS), another thermoplastic materialsuch as polycarbonate, or the like. Base 18 can also be injectionmolded, for example, out of ABS, polycarbonate, or any other suitablethermoplastic material. Each cap 14, diaphragm 16, and base 18 canindependently be three-dimensionally printed. Base 18 can beultrasonically welded to cap 14 with a portion of diaphragm 16compressed between base 18 and cap 14, to form a hermetic seal along arim 20 of POD assembly 12. As seen in FIG. 4C, diaphragm 16 has two thinhinge features 26, 28, separated by two hinge interruptions 30, 32,which together allow smooth movement and flexibility of diaphragm 16 andaccurate output of pressures, including venous pressures near zero. Cap14 comprises a sensor port 15 that can be connected, for example, bysolvent-bonding, to pressure tubing in fluid communication with apressure port of a fluid processing machine, such as a hemodialysismachine.

As seen in FIGS. 4D and 4E, base 18 has a diamond-shaped boss 22extending from the central bottom area of base 18 toward the diaphragmin an assembled POD. Boss 22 reduces the potential for blood flowocclusion caused by the diaphragm contacting the internal surface offlow-through side or chamber 24. Boss 22 forms a discontinuance in anotherwise smooth bottom surface 25 of base 18. As best seen in FIG. 4E,smooth bottom surface 25 is interrupted not only by boss 22 but also byopposing cut-outs 50 and 52 that maintain the same bottom wall shape anddepth as that provided by the bottom wall of flow path extensions 54 and56, respectively, that are in fluid communication with inlet port 38 andoutlet port 40, respectively (see also FIG. 6A).

FIG. 5 shows a top plan view of boss 220. Boss 220 has a top surface 230that faces the diaphragm in an assembled POD, i.e., in a POD assembly.Under certain pressures, top surface 230 contacts the diaphragm. Topsurface 230 is also referred to as a contacting surface and does nothave to be the uppermost surface of boss 220. For example, inorientations where the POD assembly aligns the input and output ports ofthe flow-through chamber vertically, the top surface of the boss is alsoarranged vertically and is not the most vertically uppermost part of theboss. Top surface 230 can be flat, dome shaped, curved, sloped,channeled, grooved, a combination thereof, or the like. Boss 220 canhave two sloped surfaces 240 and 250, as shown, that intersect with topsurface 230 on opposite sides of top surface 230. The intersections caneach independently be sharp, smooth, curved, angled, cornered, beveled,a combination thereof, or the like. Boss 220 can have side surfaces 260,270, 280, and 290, as shown, each of which intersects with one ofcentral sidewalls 300 and 310. The angle, ⊖₁, at the intersectiondefined by sidewall 260 and 290, can be the same as or different thanthe angle, ⊖₂, defined by the intersection of sidewalls 270 and 280.Angles ⊖₁ and ⊖₂ can each independently be within a range of from about10° to about 40°, from about 15° to about 35°, or from about 20° toabout 30°. In an exemplary embodiment, ⊖₁ and ⊖₂ are each 25.7°.

FIG. 6A is a cross-sectional side view of POD assembly 12 shown in FIG.4A. FIG. 6B is an enlarged view showing the detail of section 6B takenfrom FIG. 6A. As can be seen, elastomeric diaphragm 16 is shown in itsas-molded conformation. Elastomeric diaphragm 16 can be displaced bypressure and POD assembly 12 defines two chambers, 24 and 36, separatedby diaphragm 16. Chamber 24 is the flow-through side or chamber of thedevice. Chamber 24 is in fluid communication with two access ports,including inlet port 38 and outlet port 40. Ports 38 and 40 can besolvent-bonded to tubing in an extracorporeal blood circuit, forexample, in a hemodialysis circuit. During a dialysis treatment, bloodflows through chamber 24 in a direction from inlet port 38, through flowpath extension 54, through cut-out 50, through chamber 24, throughcut-out 52, through flow path extension 56, and to outlet port 40.

Chamber 36, also called the pressure sensing side of the POD assembly,is in fluid communication with a sensor port 42. Sensor port 42 can besolvent-bonded to tubing that includes an attached female luer fittingat an opposite end thereof. The luer fitting provides a connection forPOD assembly 12 to attach to the arterial or venous pressure port of ahemodialysis machine. The pressure port to which sensor port 42 isconnected depends on the intended use and location of POD assembly 12.

According to one or more embodiments of the present invention, themonitor line or tubing that fits into and can be solvent-bonded tosensor port 42 can include an outer sleeve at the connecting endthereof. The sleeve can have an outer diameter that matches the innerdiameter of sensor port 42. The sleeve can have an inner diameter thatmatches the outer diameter of the monitor line, for example, a diameterof 0.030 inch. As an example, the sleeve can be about 0.75 inch long andthe monitor line can be about 11 inches long.

During a dialysis treatment, diaphragm 16 is displaced by pressurechanges in the extracorporeal circuit. Displacement of the diaphragmincreases or decreases the volume of air between the diaphragm and thepressure transducer in the hemodialysis machine. Changes in air volumeproduce changes in pressure against, or acting on, the pressuretransducer. The POD assembly enables pressure monitoring of theextracorporeal circuit, without the need to have any air be in contactwith blood in the circuit. The POD assembly can be specialized to outputarterial circuit pressure, or venous circuit pressure, by setting theinitial position of diaphragm 16 during manufacture of POD assembly 12.The diaphragm also prevents blood contamination of the pressuremonitoring circuit in the dialysis machine, and prevents microbialcontamination of the blood circuit. The flow-through side 24 and thepressure sensing side 36 are designed with internal volumes thatfacilitate accurate output of arterial pressures from 0 to −300 mmHg,and venous pressures from 0 to 500 mmHg, at elevations up to 8000 feetabove sea level. Atmospheric pressure and chamber volumes can bedirectly related to a desired range of operation for accurate pressureoutput.

In one or more embodiments of the present invention, the POD assemblycan include an interrupted hinge as part of the diaphragm. The amount ofpressure required to overcome resistance to movement, of elastomericdiaphragm 16, affects the accuracy of the pressure output. As shown inFIG. 4C, two thin hinge features 26, 28 in the periphery of diaphragm 16allow smooth diaphragm displacement with minimal loss of pressure outputaccuracy. Two hinge interruptions 30, 32 are provided to separate thetwo thin hinge features 26, 28. When diaphragm 16, of a venous PODassembly, is inverted to the zero pressure start position in pressuresensing side or chamber 36, the two hinge interruptions 30, 32 producetwo small bulges along the wall of diaphragm 16. The bulges providesmooth flexibility and inverting of the diaphragm and enable accuratepressure output of venous pressures near zero, due to the fact that thebulges enable the diaphragm to exhibit very low resistance todisplacement. Bulges are described in more detail below with referenceto FIGS. 7A-8B.

When POD assembly 12 is connected to a pressure monitoring port, airpressure in flow-through side or chamber 24 slightly increases due tovolume displacement. This volume displacement occurs as a seal is formedbetween the female luer connector of the POD assembly and the male luerof the hemodialysis machine. Other suitable connectors can be used andappropriate volume displacements can be compensated for depending on theconnector type. The volume of air between diaphragm 16 and the pressuretransducer in the hemodialysis machine is also susceptible to increasesin temperature, which results in increased pressure. During a treatment,air temperature in chamber 36 increases due to blood flow, and heat canbe generated by electronics inside the hemodialysis machine, forexample, heat that can be at least partially trapped within a machineenclosure. The increased pressure caused by connecting the POD assemblyto the hemodialysis machine and the increased pressure resulting fromtemperature increases during treatment can be compensated for by the lowresistance-to-movement of the bulges. Without the bulges, the airpressure increase would add stress to diaphragm 16, and the stress inthe diaphragm would translate to a small error in pressure output,particularly at pressures near zero. The inclusion of bulges obviatesstress in the diaphragm and errors in pressure output.

FIGS. 6B and 6D are enlarged views of sections 6B and 6D shown,respectively, in FIGS. 6A and 6C. As can be seen, diaphragm 16 includesan outer peripheral grove 60 formed adjacent an outer peripheral wall 62of diaphragm 16. The outer peripheral portion of diaphragm 16, includinggrove 60 and outer peripheral wall 62, is sandwiched between cap 14 andbase 18 of POD assembly 12 (see FIGS. 6A and 6C). Cap 14 includes anouter peripheral shell rim 64 that is configured to fit into grove 60 ofdiaphragm 16. Outer peripheral shell rim 64 engages grove 60 and alsoprovides an outer surface 66 that engages outer peripheral wall 62 ofdiaphragm 16. Cap 14 also includes an outer wall 68 that, together withouter peripheral shell rim 64, forms a grove 70 that is configured toaccommodate and engage outer peripheral wall 62 of diaphragm 16. Theinterlocking arrangement between cap 14, diaphragm 16, and base 18,enable diaphragm 16 to be well seated and secured between cap 14 andbase 18.

FIGS. 7A-10B shows a venous POD assembly 120, according to one or moreembodiments of the present invention. POD assembly 120 comprises a cap114, a diaphragm 116, and a base 118. Base 118 includes an inlet port138 and an outlet port 140 that can be solvent-bonded to tubing in anextracorporeal venous blood circuit, for example, in a hemodialysiscircuit. During dialysis treatment, blood flows through flow-throughchamber 124 within the interior of POD assembly 120, in a direction frominlet port 138 toward and through outlet port 140. Cap 114 comprises asensor port 141 that can be solvent-bonded to tubing that can fluidlyconnect sensor port 141 to a venous pressure port of a hemodialysismachine. Luer fittings can also or alternatively be used to connect anyof the tubings to the POD assembly.

As shown in FIG. 7A, diaphragm 116 is at a treatment start position. Abulge 142 can be seen in diaphragm 116 and a similar bulge is providedin the other half (not shown) of diaphragm 116. Bulges 142 can be causedby hinge interruptions 130, 132 as shown in FIG. 7B. Hinge interruptions130, 132 divide a peripheral hinge along the periphery of diaphragm 116into two hinge features 126, 128. Greater details regarding hingefeatures 126, 128 and hinge interruptions 130, 132 can be discerned withreference to FIGS. 6B and 6D and the description of hinge feature 28 andhinge interruption 32 shown therein. In one or more embodiments, hingefeatures 126, 128 can be identical to hinge feature 28 described in FIG.6B. In one or more embodiments, hinge interruptions 130, 132 can beidentical to hinge interruptions 32 shown in FIG. 6D.

FIGS. 8A and 8B show venous POD assembly 120 illustrated in FIGS. 7A and7B but wherein bulges 142, shown in FIGS. 7A and 7B, have been displacedand no longer exist along diaphragm 116. Locations 144 shown in FIGS. 8Aand 8B indicate where bulges 142 had occurred in diaphragm 116, but aredisplaced due to a near zero pressure condition. Before being connectedto a venous pressure port of the hemodialysis machine, bulges 142 canexist in diaphragm 116, but can be displacement upon connection of PODassembly 120 to the venous pressure port. The displacement can occur dueto the very small increase in pressure within pressure-sensing side orchamber 136, resulting from the act of connecting the tubing from sensorport 141 of POD assembly 120 to the venous pressure port of thehemodialysis machine. Bulges 142 in diaphragm 116 can compensate forthis very minor increase in pressure and can thus enable positioning ofdiaphragm 116 at the start of a treatment such that POD assembly 120 canvery accurately measure a full range of expected pressures within thevenous circuit.

With reference to FIGS. 7A-10B, a pressure output device (POD) assembly120 is shown. POD assembly 120 can comprise a diamond-shaped boss 122that can reduce, minimize, or substantially minimize the potential forhemolysis due to occlusion of blood flow through the POD assembly. Ascan be seen, diamond-shaped boss 122 extends into flow-through chamber124. When POD assembly 120 is used to output negative pressure in anarterial blood circuit, fault conditions can displace diaphragm 116 intochamber 124 to an extent such that diaphragm 116 contacts and pushesbelow facing surface 123 of boss 122. When this occurs, diaphragm 116partially deforms around boss 122 as shown in FIGS. 9A-10B, thuspreventing diaphragm 116 from fully contacting an internal surface 125of chamber 124. Without boss 122, diaphragm 116 could substantiallyfully and/or flushly contact internal surface 125. Full and flushcontact would present various levels of occlusion to blood flow but suchcontact is avoided according to one or more embodiments of the presentinvention.

As can be seen in FIG. 10B, rather than occluding blood flow under theextreme pressure condition shown, boss 122 props-up, like a tent pole,diaphragm 116 and forms a blood flow path 150 arranged adjacent the sidewalls of boss 122 and through chamber 124, and boss 122 preventsoccluding of blood flow path 150. Furthermore, the provision of verticalsidewall portions 152 and 154 in base 118 also provide flow-throughspaces such as at 156 so that the blood flow path is not occluded.

As shown in FIGS. 11A-11C, a POD base 218, in accordance with one ormore embodiments of the present invention, is provided. POD base 218comprises an inlet port 238, an outlet port 240, a smooth bottom wall225, a pair of opposing cut-outs, 250 and 252, formed in bottom wall225, and flow path extensions 254 and 256, respectively, that are influid communication with inlet port 238 and outlet port 240,respectively. Cut-outs 250 and 252 each have a bottom that maintains thesame bottom wall shape and depth as provided by the bottom of flow pathextensions 254 and 256, respectively. Flow path extension 254 can havethe same depth as cut-out 250 and the two features can be separated by aneck, as best seen in FIG. 11B. Similarly, flow path extension 256 canhave the same depth as cut-out 252 and the two features can be separatedby a neck. Blood tubing having an outer diameter that is the same as theinner diameter of a flow path extension can be inserted into the flowpath extension and solvent bonded therein.

POD base 218 can be provided with a vertical wall extension 230. Smoothbottom wall 225 intersects with vertical wall extension 230 along acircle 232. As can be seen in FIGS. 11D and 11E, POD base 218 can beassembled with a cap 214 and a diaphragm 216 to form a POD assembly 212defining a flow-through chamber 224 and a pressure sensing chamber 236.Vertical wall extension 230 can be of any suitable height, and can beincluded to maintain a diaphragm, such as diaphragm 216 shown in FIGS.11D and 11E, above and spaced from bottom wall 225, for example, toprevent diaphragm 216 from contacting bottom wall 225 and occluding flowthrough flow-through chamber 224 of POD assembly 212. As shown, cut-outs250 and 252 can be formed completely in bottom wall 225, and not invertical wall extension 230. In some embodiments, the cut-outs can alsobe defined, at least in-part, by vertical wall extension 230.

A rim 220 is formed near the outer periphery of POD base 218, which canform a hermetic seal with a diaphragm, as shown in the assembled PODassembly illustrated in FIGS. 11D and 11E. POD base 218 can be injectionmolded, for example, out of ABS, polycarbonate, or any other suitablethermoplastic material. POD base 218 can be three-dimensionally printed.POD base 218 can be ultrasonically welded to cap 214, as shown in FIGS.11D and 11E, with the periphery of diaphragm 216 compressed between PODbase 218 and cap 214, to form a hermetic seal along rim 220. Cap 214comprises a sensor port 242 that can be connected, for example, bysolvent-bonding, to pressure tubing that can be made to be in fluidcommunication with a pressure port of a fluid processing machine, suchas a hemodialysis machine.

FIGS. 12A-12C show yet another POD assembly according to one or moreembodiments of the present invention, and configured to monitor venouspressure. In FIGS. 12A-12C, a POD assembly 312, in accordance with oneor more embodiments of the present invention, is shown. POD assembly 312includes a POD base 318, a POD cap 314, and a diaphragm 316 pinched andheld between POD base 318 and POD cap 314. POD base 318 comprises aninlet port 338, an outlet port 340, a smooth bottom wall 325, flow pathextensions 354 and 356, bypass channel portions 350 and 352, an inletchamber port 360, and an outlet chamber port 362. Flow path extensions354 and 356 are in fluid communication with inlet port 338 and outletport 340, respectively. A bypass channel is provided that comprises flowpath extension 354, bypass channel portion 350, bypass channel portion352, and flow path extension 356. Inlet chamber port 360 is in fluidcommunication with bypass channel portion 350 and a flow-through chamber324 defined between POD base 318 and diaphragm 316. Outlet chamber port362 is in fluid communication with bypass channel portion 352 andflow-through chamber 324. While blood can flow into and out offlow-through chamber 324, blood can also bypass chamber 324 through thebypass channel. In the event of an occlusion of flow throughflow-through chamber 324, blood can still flow into inlet port 338 andout outlet port 340. Cap 314 comprises a sensor port 342 that can beconnected, for example, by solvent-bonding, to pressure tubing that canbe made to be in fluid communication with a pressure port of ahemodialysis machine.

As can be seen best in FIG. 12A, bypass channel portion 350 narrows fromits intersection with flow path extension 354 toward its intersectionwith bypass channel portion 352. Similarly, bypass channel portion 352narrows from its intersection with flow path extension 356 toward itsintersection with bypass channel portion 350. The narrowing of thebypass channel portions influences the flow of blood through the bypasschannel such that a portion of the flow is directed into flow-throughchamber 324 and the pressure of blood flowing through the bypass channeland through flow-through chamber 324 can be sensed.

FIG. 12B shows the same POD assembly 312 shown in FIGS. 12A and 12C, butwherein the diaphragm is positioned adjacent the inside of cap 314 suchthat the POD assembly is configured for sensing arterial pressure. FIG.12C is a cross-sectional end view of FIG. 12A, wherein, just as is shownin FIG. 12A, POD assembly 312 is configured for sensing venous pressure.

FIG. 13 shows yet another POD assembly according to one or moreembodiments of the present invention, and configured for sensingarterial pressure. In FIG. 13, a POD assembly 412 is shown and comprisesa cap 414, a base 418, and a telescoping diaphragm 416 pinched and heldbetween cap 414 and base 418. Diaphragm 416 separates the interior ofPOD assembly 412 into a flow-through chamber 424 below the diaphragm anda pressure sensing chamber 436 above the diaphragm. Flow-through chamber424 is in fluid communication with an inlet and an outlet, and theoutlet shown includes a flow path extension 452. Diaphragm 416 includesa circular hinge 420 defining a circle at which a top dome 422 ofdiaphragm 416 can pivot between a popped-in configuration as shown and apopped-out configuration (not shown) where dome 422 is adjacent theinside top surface of cap 414. Hinge 420 enables a smooth change betweenthe popped-in and popped-out configurations so that pressure can beaccurately sensed even in pressure ranges just below or just above thepressures that cause a popping-in or a popping-out action. Thus,accurate arterial pressures can be sensed over the entire range ofarterial pressures to which the diaphragm is expected to be exposedduring a hemodialysis treatment.

FIGS. 14 and 15 show yet another POD assembly according to one or moreembodiments of the present invention. In FIG. 14, POD assembly 512 isconfigured for sensing arterial pressure. In FIG. 15, two alternativestarting positions of the diaphragm are shown. POD assembly 512comprises a cap 514, a base 518, and a telescoping diaphragm 516 pinchedand held between cap 514 and base 518. Diaphragm 516 separates theinterior of POD assembly 512 into a flow-through chamber 524 below thediaphragm and a pressure sensing chamber 525 above the diaphragm.Flow-through chamber 524 is in fluid communication with an inlet and anoutlet, and the outlet shown includes a flow path extension 552.Diaphragm 516 includes a plurality of circular hinges, including hinges530 and 532, which define respective circles at which one or moresegments of diaphragm 516 can pivot. For example, diaphragm 516 can bedivided into a base segment 520, intermediate segments 522, 534, and536, and a top segment or dome 538. Segments 520 and 522 can pivot withrespect to one another along hinge 530. Segments 522 and 534 can pivotwith respect to one another along hinge 532. The entirety of diaphragm516 can also be inverted, as shown by the bottom diaphragm positionillustrated in FIG. 15.

The plurality of segments and plurality of hinges enable a smooth changebetween popped-in and popped-out configurations so that pressure can beaccurately sensed even in pressure ranges just below or just above thepressures that cause a popping-in or a popping-out action. Thus, for thearterial configuration, specifically, as shown in FIG. 14, accuratearterial pressures can be sensed over the entire range of arterialpressures to which the diaphragm is expected to be exposed during ahemodialysis treatment. For the venous configuration, specifically, asshown in FIG. 15 with the diaphragm at the bottom position, accuratevenous pressures can be sensed over the entire range of venous pressuresto which the diaphragm is expected to be exposed during a hemodialysistreatment.

According to one of more embodiments of the present invention, thediaphragm position within the POD assembly can be adjusted and set suchthat a user can set the amount of negative versus positive pressure thatthe POD assembly can sense. A pressure monitoring machine, for example,a hemodialysis machine, can be provided with a pneumatic cylinder thatis in fluid communication with the pressure sensing chamber or side ofthe POD assembly. A three-way valve can be provided in fluidcommunication with the pneumatic cylinder and can be opened to enablethe pressure within the pneumatic cylinder to equilibrate with thesurrounding ambient air pressure. The pneumatic cylinder can have agreater volume than the volume inside the interior of the POD assembly,for example, at least 1.5 times as large, or at least two times aslarge, as the interior volume of the POD assembly. A piston within thepneumatic cylinder can be placed at a mid-point position. The three-wayvalve can then be closed to isolate the pneumatic cylinder from thesurrounding environment, to enable the pneumatic cylinder to be inpneumatic contact with the POD assembly diaphragm, and to form a fluidcommunication between the pneumatic cylinder and the pressure sensingchamber of the POD assembly. Next, the piston within the cylinder can beadvanced until a pressure gauge reading of 1 psi is achieved, at whichpoint the position of the piston within the cylinder can be recorded.The piston can be then retracted in the cylinder until the pressuregauge achieves a reading of −1 psi, at which point the piston positioncan be recorded. The mid-point between the two recorded positions of thepiston within the pneumatic cylinder can be established as a mid-pointof the POD assembly diaphragm. The diaphragm can be positionedaccordingly and the three-way valve can be closed-off to preserve theposition of the diaphragm. Other positions of the piston, positionsaligned with graduated indicia, or the like, can be used to calibratethe POD assembly diaphragm position and enable accurate pressure sensingover a desired pressure range.

According to one or more embodiments of the present invention, a pair ofPOD assemblies, one for sensing arterial pressure and one for sensingvenous pressure, can be included in a blood tubing set that is intendedto be used with a Fresenius Medical Care 2008® Series K, K2, or THemodialysis Machine. The POD assemblies shown in FIGS. 1A-2C and 4A-10Bare exemplary. The machine can be equipped with a level detector modulefor standard air-detection compliance and equipped with an air detectormodule for enhanced micro-bubble detection compliance. The bloodline canbe part of an extracorporeal circuit by which blood is transported fromthe patient through a hemodialyzer (for cleansing), and back to thepatient. The pump segment in the bloodline interfaces to the blood pumprotor mechanism on the hemodialysis machine, which drives the flow ofblood through the circuit. The bloodline contains interfaces to thehemodialysis machine safety mechanism to ensure proper operation. Theseinterfaces can be for POD monitor lines for monitoring arterial andvenous pressures, as well as for a venous chamber for the detection ofair in the blood path. The Arterial pressure measurement POD can bemounted flush with the inlet-side pump housing.

In use, an operator can calibrate the blood pump for 8 mm pump segmentsaccording to the 2008® Series K, K2, and T Hemodialysis MachineOperator's Instructions. The actual blood flow rate may differ from theblood flow rate indicated by the machine and may change with time.Actual blood flow is affected by arterial and venous pressures,hematocrit, AV fistula needle size, and other factors.

To spike a saline bag, the operator can remove the spike protectorwithout touching the spike and insert the spike through the port on thesaline bag. Prior to priming, the operator can ensure that the PODflexible diaphragms are in their correct positions. In general, thearterial diaphragm is curved towards the dome side or cap of the POD.The venous diaphragm is curved towards the base side of the POD.

To correct a mis-positioned diaphragm, a 5 mL (or larger) syringe can beused to inject or extract air though the pressure tubing or monitor lineto move the diaphragm to the appropriate position. The diaphragm mayreadjust slightly when the syringe is removed.

During treatment, the arterial POD can run approximately full to ½ full,and the venous POD can run approximately ¼ full to ¾ full. The PODdiaphragms will pulsate and change position slightly during treatment.Significant diaphragm position changes can cause incorrect pressurereadings and can require corrective action. An operator can correct adiaphragm if either the arterial or venous diaphragm contacts the baseor boss, or if the venous diaphragm contacts greater than ¾ of the domesurface during diaphragm pulsation.

To correct a mis-positioned arterial diaphragm during treatment due toan arterial pressure alarm or a zero arterial pressure reading, thefollowing steps can be taken. The operator can stop the blood pump,close the arterial patient clamp, and reset the alarms if necessary. Theoperator can disconnect the arterial monitor line from the machinepressure port and allow the diaphragm to return to its correct position.Saline administration and saline “T” clamps can be opened if necessary.The operator can reattach the monitor line to the machine pressure portand close the saline administration and saline “T” clamps. The operatorcan then open the arterial patient clamp, restart the blood pump, andobserve to verify the correct diaphragm position and appropriatepressure reading. After making an arterial POD diaphragm adjustment, theoperator can ensure that the arterial monitor line connection to themachine port is secure.

To correct a mis-positioned venous diaphragm during treatment due to avenous pressure alarm, a TMP alarm, or a zero venous pressure reading,the following steps can be taken. The operator can press Reset to resetthe alarm, stop the blood pump, press the Reset key again, and hold itfor two seconds to select new alarm limits. The operator can press the▾level key on the machine venous module until the diaphragm ispositioned to just touch the base side boss and then use the ▴leveladjust key to then move the diaphragm back slightly until it no longertouches the boss. Then, the operator can restart the blood pump andobserve to verify the correct diaphragm position and appropriatepressure reading.

In some cases, to correct a mis-positioned venous diaphragm duringtreatment due to a venous pressure alarm, a TMP alarm or a zero venouspressure reading, the following steps can be taken. The operator canstop the blood pump, close the venous monitor line clamp, and reset thealarms if necessary. The operator can disconnect the venous monitor linefrom machine pressure port, connect a 5 mL (or larger) syringe, withplunger pulled back, to the venous monitor line, open the monitor clamp,and inject up to 4 mL of air until the diaphragm is positioned to justtouch the base side boss. The operator can pull back on the plunger tothen move the diaphragm back slightly until it no longer touches theboss. After that, the operator can close the monitor line clamp, removethe syringe, reattach the monitor line to the machine pressure port,open the clamp, and restart the pump. The operator can then observe toverify the correct diaphragm position and appropriate pressure reading.After making venous POD diaphragm adjustments the operator can ensurethe venous monitor line connection to the machine port is secure.

The dialyzer can be primed according to the machine manufacturer'sinstructions. If the instructions require clamping bloodlines, thepressure-monitoring lines should be unclamped before occluding thebloodlines, to prevent excessive dialyzer pressures.

The venous chamber fluid level can be established by purging air througha venous chamber “pigtail” access site. An operator can open the“pigtail” clamp and loosen the cap. When air is removed, and both thechamber and “pigtail” are full, the operator can then clamp the line andtighten the cap.

To set up the blood lines, an operator can first ensure the DialyzerHolder Lock Sleeve is installed onto the dialyzer holder in accordancewith the Dialyzer Holder Lock Sleeve mounting instructions for themachine. The operator can push the dialyzer into the holder, arterialend down, with the clamp in the middle of the dialyzer, then positionthe dialysate ports to the right, facing outwardly away from themachine.

For the arterial line, the operator can close the heparin line clamp,then ensure the arterial POD diaphragm is correctly positioned towardthe dome side or cap. The blood pump segment can then be inserted intothe blood pump. The operator can ensure the segment with the arterialPOD is threaded to the left side of the blood pump housing with themonitoring line facing forward, away from the machine. The machine doorcan then be closed. Next, the operator can connect the dialyzer end ofthe arterial line to the bottom/arterial port of the dialyzer, andensure the connection to the port is finger tight. The operator can thenaseptically place the patient end of the arterial line into a primingbucket clip.

For the venous line, the operator can close the venous chamber “pigtail”access site clamp. The operator can ensure the venous POD diaphragm iscorrectly positioned toward the base side of the POD. Next, the operatorcan roll the venous drip chamber into the venous level detector with thefilter located below the sensor heads. Next, the operator can connectthe dialyzer end of the venous line to the top/venous port of thedialyzer, and position the venous POD so that the dome side or cap isfacing forward. The operator can ensure the connection to the port isfinger tight. Next, the operator can clamp the venous POD monitor line,leave it disconnected from the machine, and aseptically place thepatient end of the venous line into the priming bucket clip. Priming ofthe extracorporeal circuit can require approximately 300 mL of saline,depending on the size and model of the dialyzer.

During treatment, the arterial and venous pressures can be routinelymonitored. Pressure readings which are clinically inappropriate (e.g. 0mmHg) can be addressed immediately as these may indicate a POD monitorline is clamped, kinked, not attached securely, or that the PODdiaphragm is not in the correct position.

The present invention includes the following numbered aspects,embodiments, and features, in any order and/or in any combination:

1. A pressure output device for sensing fluid pressure in a fluidprocessing system, the pressure sensing device comprising:

a shell defining a shell interior; and

a movable diaphragm disposed in the shell interior and separating theshell interior into a flow-through chamber defined by a lower portion ofthe shell and a first side of the diaphragm, and a pressure sensingchamber defined by an upper portion of the shell and a second side ofthe diaphragm, the second side being opposite the first side, the shellfurther defining a sensor port in fluid communication with the pressuresensing chamber, an inlet port in fluid communication with theflow-through chamber, and an outlet port in fluid communication with theflow-through chamber,

wherein the inlet port and the outlet port define an inlet and anoutlet, respectively, of a fluid flow path through the flow-throughchamber, and the flow-through chamber has an interior wall and comprisesa boss along the interior wall, which prevents the diaphragm fromoccluding flow through the fluid flow path.

2. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the inlet port has an axial center,the outlet port has an axial center, the axial center of the inlet portis substantially or completely aligned with the axial center of theoutlet port, the boss protrudes from the interior wall and extends intothe fluid flow path, and the boss includes at least one feature thatintersects with a line that is co-axial with one or both of the axialcenters.3. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the fluid processing system is ahemodialysis machine, the fluid path is a blood path, and the bosscomprises a diamond-shaped cross-section configured to minimize thepotential for hemolysis due to occlusion of blood flow.4. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the boss comprises a mid-section, afirst end adjacent the inlet port, and a second end adjacent the outletport, and the boss has a thickness that increases in a direction fromthe first end toward the mid-section and a thickness that increases in adirection from the second end toward the mid-section.5. The pressure output devices of any preceding or followingembodiment/feature/aspect, wherein the boss has a width that increasesin a direction from the first end toward the mid-section and a widththat increases in a direction from the second end toward themid-section.6. A system comprising the pressure output device of any preceding orfollowing embodiment/feature/aspect, a pressure monitor, and a monitorline that forms a fluid communication between the sensor port and thepressure monitor.7. A system comprising the pressure output device of any preceding orfollowing embodiment/feature/aspect, a first blood tubing in fluidcommunication with the inlet port, a second blood tubing in fluidcommunication with the outlet port, and a blood pump in operativeengagement with at least one of the first blood tubing and the secondblood tubing.8. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the shell comprises a shell top and ashell bottom, the movable diaphragm comprises an outer periphery, andthe outer periphery is sandwiched between the shell top and the shellbottom.9. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the outer periphery of the movablediaphragm includes a groove, and at least one of the shell top and theshell bottom includes an outer peripheral shell rim configured to fitinto the groove and engage the outer periphery of the movable diaphragm.10. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the shell top and the shell bottomare bonded together, the movable diaphragm is positioned between theshell top and the shell bottom, and the outer peripheral rim is seatedin the groove of the movable diaphragm.11. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the groove is formed on a first sideof the movable diaphragm, the outer periphery of the movable diaphragmcomprises a rim along a second side of the movable diaphragm oppositethe first side, the shell top comprises the outer peripheral shell rim,and the shell bottom comprises an outer peripheral groove configured toaccommodate and engage the rim of the movable diaphragm.12. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the diaphragm comprises a peripheralhinge and one or more hinge interruptions that form one or morerespective discontinuances along the peripheral hinge.13. A pressure output device for sensing fluid pressure in a fluidprocessing system, the pressure sensing device comprising:

a shell defining a shell interior; and

a movable diaphragm disposed in the shell interior and separating theshell interior into a flow-through chamber defined by a lower portion ofthe shell and a first side of the diaphragm, and a pressure sensingchamber defined by an upper portion of the shell and a second side ofthe diaphragm, the second side being opposite the first side, the shellfurther defining a sensor port in fluid communication with the pressuresensing chamber, an inlet port in fluid communication with theflow-through chamber, and an outlet port in fluid communication with theflow-through chamber, the inlet port and the outlet port being alignedwith one another along a first line,

wherein the inlet port and the outlet port define an inlet and anoutlet, respectively, of a fluid flow path through the flow-throughchamber, the flow-through chamber comprises an interior shell wallhaving a mid-section that includes a smooth uninterrupted surface thatis continuous from a first point on the interior shell wall at a firstintersection with the diaphragm to a second point on the interior shellwall at a second intersection with the diaphragm, the first and secondpoints are arranged along a line that is perpendicular to the firstline, the inlet of the fluid flow path merges with the smoothuninterrupted surface of the interior shell wall at a first partialinterior shell wall cut-out, the outlet of the fluid flow path mergeswith the smooth uninterrupted surface of the interior shell wall at asecond partial interior shell wall cut-out, the fluid flow path includesthe first partial interior shell wall cut-out, the interior shell wallmid-section, and the second partial interior shell wall cut-out, and thefirst and second interior shell wall cut-outs do not intersect with oneanother.

14. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the inlet port has an axial center,the outlet port has an axial center, and the axial center of the inletport is substantially or completely aligned with the axial center of theoutlet port.15. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the fluid processing system is ahemodialysis machine, the fluid flow path is a blood flow path, and thefluid flow path is configured to minimize the potential for hemolysisdue to occlusion of blood flow.16. A system comprising the pressure output device of any preceding orfollowing embodiment/feature/aspect, a pressure monitor, and a monitorline that forms a fluid communication between the sensor port and thepressure monitor.17. A system comprising the pressure output device of any preceding orfollowing embodiment/feature/aspect, a first blood tubing in fluidcommunication with the inlet port, a second blood tubing in fluidcommunication with the outlet port, and a blood pump in operativeengagement with at least one of the first blood tubing and the secondblood tubing.18. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the shell comprises a shell top and ashell bottom, the movable diaphragm comprises an outer periphery, andthe outer periphery is sandwiched between the shell top and the shellbottom.19. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the outer periphery of the movablediaphragm includes a groove, and at least one of the shell top and theshell bottom includes an outer peripheral shell rim configured to fitinto the groove and engage the outer periphery of the movable diaphragm.20. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the shell top and the shell bottomare bonded together, the movable diaphragm is positioned between theshell top and the shell bottom, and the outer peripheral rim is seatedin the groove of the movable diaphragm.21. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the groove is formed on a first sideof the movable diaphragm, the outer periphery of the movable diaphragmcomprises a rim along a second side of the movable diaphragm oppositethe first side, the shell top comprises the outer peripheral shell rim,and the shell bottom comprises an outer peripheral groove configured toaccommodate and engage the rim of the movable diaphragm.22. A pressure output device for sensing fluid pressure in a fluidprocessing system, the pressure sensing device comprising:

a shell defining a shell interior; and

a movable diaphragm disposed in the shell interior and separating theshell interior into a flow-through chamber defined by a lower portion ofthe shell and a first side of the diaphragm, and a pressure sensingchamber defined by an upper portion of the shell and a second side ofthe diaphragm, the second side being opposite the first side, the shellfurther defining an interior bottom wall of the flow-through chamber, asensor port in fluid communication with the pressure sensing chamber, abypass channel separated from the flow-through chamber and formedunderneath the interior bottom wall, an inlet chamber port that forms afirst fluid communication between the flow-through chamber and thebypass channel, and an outlet chamber port that forms a second fluidcommunication between the flow-through chamber and the bypass channel,

wherein the bypass channel comprises an inlet port adjacent the inletchamber port and configured to connect to an incoming blood line, and anoutlet port adjacent the outlet chamber port and configured to connectto an outgoing blood line, and the bypass channel provides anon-occluded blood flow path from the inlet port to the outlet port evenif the diaphragm completely occludes blood flow through the flow-throughchamber.23. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the bypass channel has a firstdiameter at the inlet port and a second, smaller diameter, between theinlet chamber port and the outlet chamber port.24. The pressure output device of any preceding or followingembodiment/feature/aspect, wherein the bypass channel has a thirddiameter at the outlet port, which is larger than the second diameterbetween the inlet chamber port and the outlet chamber port.25. A system comprising the pressure output device of any preceding orfollowing embodiment/feature/aspect, and a hemodialysis machine, thehemodialysis machine comprising a pressure monitor, wherein the systemfurther comprises a pressure monitor line that forms a fluidcommunication between the sensor port and the pressure monitor.26. A system comprising the pressure output device of any preceding orfollowing embodiment/feature/aspect, a first blood tubing in fluidcommunication with the inlet port, a second blood tubing in fluidcommunication with the outlet port, and a blood pump in operativeengagement with at least one of the first blood tubing and the secondblood tubing, wherein the diaphragm is configured such that at apressure of −300 mmHg the diaphragm approaches but does not contact theinterior bottom wall of the flow-through chamber.

The present invention can include any combination of these variousfeatures or embodiments above and/or below as set forth in sentencesand/or paragraphs. Any combination of disclosed features herein isconsidered part of the present invention and no limitation is intendedwith respect to combinable features.

The entire contents of all references cited in this disclosure areincorporated herein in their entireties, by reference. Further, when anamount, concentration, or other value or parameter is given as either arange, preferred range, or a list of upper preferable values and lowerpreferable values, this is to be understood as specifically disclosingall ranges formed from any pair of any upper range limit or preferredvalue and any lower range limit or preferred value, regardless ofwhether such ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. It is not intended that the scope of the invention be limitedto the specific values recited when defining a range.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

What is claimed is:
 1. A pressure output device for sensing fluidpressure in a fluid processing system, the pressure sensing devicecomprising: a shell defining a shell interior; and a movable diaphragmdisposed in the shell interior and separating the shell interior into aflow-through chamber defined by a lower portion of the shell and a firstside of the diaphragm, and a pressure sensing chamber defined by anupper portion of the shell and a second side of the diaphragm, thesecond side being opposite the first side, the shell further defining asensor port in fluid communication with the pressure sensing chamber, aninlet port in fluid communication with the flow-through chamber, and anoutlet port in fluid communication with the flow-through chamber,wherein the inlet port and the outlet port define an inlet and anoutlet, respectively, of a fluid flow path through the flow-throughchamber, and the flow-through chamber has an interior wall and comprisesa boss along the interior wall, which prevents the diaphragm fromoccluding flow through the fluid flow path.
 2. The pressure outputdevice of claim 1, wherein the inlet port has an axial center, theoutlet port has an axial center, the axial center of the inlet port issubstantially or completely aligned with the axial center of the outletport, the boss protrudes from the interior wall and extends into thefluid flow path, and the boss includes at least one feature thatintersects with a line that is co-axial with one or both of the axialcenters.
 3. The pressure output device of claim 1, wherein the fluidprocessing system is a hemodialysis machine, the fluid path is a bloodpath, and the boss comprises a diamond-shaped cross-section configuredto minimize the potential for hemolysis due to occlusion of blood flow.4. The pressure output device of claim 1, wherein the boss comprises amid-section, a first end adjacent the inlet port, and a second endadjacent the outlet port, and the boss has a thickness that increases ina direction from the first end toward the mid-section and a thicknessthat increases in a direction from the second end toward themid-section.
 5. The pressure output devices of claim 4, wherein the bosshas a width that increases in a direction from the first end toward themid-section and a width that increases in a direction from the secondend toward the mid-section.
 6. A system comprising the pressure outputdevice of claim 1, a pressure monitor, and a monitor line that forms afluid communication between the sensor port and the pressure monitor. 7.A system comprising the pressure output device of claim 1, a first bloodtubing in fluid communication with the inlet port, a second blood tubingin fluid communication with the outlet port, and a blood pump inoperative engagement with at least one of the first blood tubing and thesecond blood tubing.
 8. The pressure output device of claim 1, whereinthe shell comprises a shell top and a shell bottom, the movablediaphragm comprises an outer periphery, and the outer periphery issandwiched between the shell top and the shell bottom.
 9. The pressureoutput device of claim 8, wherein the outer periphery of the movablediaphragm includes a groove, and at least one of the shell top and theshell bottom includes an outer peripheral shell rim configured to fitinto the groove and engage the outer periphery of the movable diaphragm.10. The pressure output device of claim 9, wherein the shell top and theshell bottom are bonded together, the movable diaphragm is positionedbetween the shell top and the shell bottom, and the outer peripheral rimis seated in the groove of the movable diaphragm.
 11. The pressureoutput device of claim 9, wherein the groove is formed on a first sideof the movable diaphragm, the outer periphery of the movable diaphragmcomprises a rim along a second side of the movable diaphragm oppositethe first side, the shell top comprises the outer peripheral shell rim,and the shell bottom comprises an outer peripheral groove configured toaccommodate and engage the rim of the movable diaphragm.
 12. Thepressure output device of claim 1, wherein the diaphragm comprises aperipheral hinge and one or more hinge interruptions that form one ormore respective discontinuances along the peripheral hinge.
 13. Apressure output device for sensing fluid pressure in a fluid processingsystem, the pressure sensing device comprising: a shell defining a shellinterior; and a movable diaphragm disposed in the shell interior andseparating the shell interior into a flow-through chamber defined by alower portion of the shell and a first side of the diaphragm, and apressure sensing chamber defined by an upper portion of the shell and asecond side of the diaphragm, the second side being opposite the firstside, the shell further defining a sensor port in fluid communicationwith the pressure sensing chamber, an inlet port in fluid communicationwith the flow-through chamber, and an outlet port in fluid communicationwith the flow-through chamber, the inlet port and the outlet port beingaligned with one another along a first line, wherein the inlet port andthe outlet port define an inlet and an outlet, respectively, of a fluidflow path through the flow-through chamber, the flow-through chambercomprises an interior shell wall having a mid-section that includes asmooth uninterrupted surface that is continuous from a first point onthe interior shell wall at a first intersection with the diaphragm to asecond point on the interior shell wall at a second intersection withthe diaphragm, the first and second points are arranged along a linethat is perpendicular to the first line, the inlet of the fluid flowpath merges with the smooth uninterrupted surface of the interior shellwall at a first partial interior shell wall cut-out, the outlet of thefluid flow path merges with the smooth uninterrupted surface of theinterior shell wall at a second partial interior shell wall cut-out, thefluid flow path includes the first partial interior shell wall cut-out,the interior shell wall mid-section, and the second partial interiorshell wall cut-out, and the first and second interior shell wallcut-outs do not intersect with one another.
 14. The pressure outputdevice of claim 13, wherein the inlet port has an axial center, theoutlet port has an axial center, and the axial center of the inlet portis substantially or completely aligned with the axial center of theoutlet port.
 15. The pressure output device of claim 13, wherein thefluid processing system is a hemodialysis machine, the fluid flow pathis a blood flow path, and the fluid flow path is configured to minimizethe potential for hemolysis due to occlusion of blood flow.
 16. A systemcomprising the pressure output device of claim 13, a pressure monitor,and a monitor line that forms a fluid communication between the sensorport and the pressure monitor.
 17. A system comprising the pressureoutput device of claim 13, a first blood tubing in fluid communicationwith the inlet port, a second blood tubing in fluid communication withthe outlet port, and a blood pump in operative engagement with at leastone of the first blood tubing and the second blood tubing.
 18. Thepressure output device of claim 13, wherein the shell comprises a shelltop and a shell bottom, the movable diaphragm comprises an outerperiphery, and the outer periphery is sandwiched between the shell topand the shell bottom.
 19. The pressure output device of claim 13,wherein the outer periphery of the movable diaphragm includes a groove,and at least one of the shell top and the shell bottom includes an outerperipheral shell rim configured to fit into the groove and engage theouter periphery of the movable diaphragm.
 20. The pressure output deviceof claim 19, wherein the shell top and the shell bottom are bondedtogether, the movable diaphragm is positioned between the shell top andthe shell bottom, and the outer peripheral rim is seated in the grooveof the movable diaphragm.
 21. The pressure output device of claim 19,wherein the groove is formed on a first side of the movable diaphragm,the outer periphery of the movable diaphragm comprises a rim along asecond side of the movable diaphragm opposite the first side, the shelltop comprises the outer peripheral shell rim, and the shell bottomcomprises an outer peripheral groove configured to accommodate andengage the rim of the movable diaphragm.
 22. A pressure output devicefor sensing fluid pressure in a fluid processing system, the pressuresensing device comprising: a shell defining a shell interior; and amovable diaphragm disposed in the shell interior and separating theshell interior into a flow-through chamber defined by a lower portion ofthe shell and a first side of the diaphragm, and a pressure sensingchamber defined by an upper portion of the shell and a second side ofthe diaphragm, the second side being opposite the first side, the shellfurther defining an interior bottom wall of the flow-through chamber, asensor port in fluid communication with the pressure sensing chamber, abypass channel separated from the flow-through chamber and formedunderneath the interior bottom wall, an inlet chamber port that forms afirst fluid communication between the flow-through chamber and thebypass channel, and an outlet chamber port that forms a second fluidcommunication between the flow-through chamber and the bypass channel,wherein the bypass channel comprises an inlet port adjacent the inletchamber port and configured to connect to an incoming blood line, and anoutlet port adjacent the outlet chamber port and configured to connectto an outgoing blood line, and the bypass channel provides anon-occluded blood flow path from the inlet port to the outlet port evenif the diaphragm completely occludes blood flow through the flow-throughchamber.
 23. The pressure output device of claim 22, wherein the bypasschannel has a first diameter at the inlet port and a second, smallerdiameter, between the inlet chamber port and the outlet chamber port.24. The pressure output device of claim 23, wherein the bypass channelhas a third diameter at the outlet port, which is larger than the seconddiameter between the inlet chamber port and the outlet chamber port. 25.A system comprising the pressure output device of claim 22 and ahemodialysis machine, the hemodialysis machine comprising a pressuremonitor, wherein the system further comprises a pressure monitor linethat forms a fluid communication between the sensor port and thepressure monitor.
 26. A system comprising the pressure output device ofclaim 22, a first blood tubing in fluid communication with the inletport, a second blood tubing in fluid communication with the outlet port,and a blood pump in operative engagement with at least one of the firstblood tubing and the second blood tubing, wherein the diaphragm isconfigured such that at a pressure of −300 mmHg the diaphragm approachesbut does not contact the interior bottom wall of the flow-throughchamber.